Patients suffering from aortic valve stenosis often have calcified aortic valve leaflets. Shockwave therapy for the treatment of aortic valve stenosis has been previously described in, for example U.S. Pat. Pub. No. 2010/0114020A1, the disclosure of which is incorporated herein by reference. As described therein, a valvuloplasty catheter includes a balloon that is inflatable with a fluid. When the balloon is inflated, it is configured to be adjacent valve leaflets, such as the valve leaflets of an aortic valve. Within the balloon, there is disposed a shock wave generator. The shock wave generator includes at least two electrodes. When a high voltage pulse is applied across the electrodes, an electrical arc is formed. The electrical arc creates a shock wave within the fluid that propagates to the balloon walls to impinge upon the valve leaflets and the calcification on the valve. Repeated shock waves cause the calcification to break-up.
The distance between the shock wave generator (the electrodes) and the valve leaflets of the catheter described above is variable and not controlled. It has been found that shock wave therapy designed to break calcium deposits is most effective at certain distances from a radiating shock wave source. This is particularly the case when the source is a point source without a reflector. Generally, the effectiveness of the shock waves falls off or decreases with the square of the distance from the source.
When a valvuloplasty balloon and a shock wave generator are combined as described above, the distance between the shock wave generator and the balloon walls generally increases as the valve is opened by balloon expansion occasioned by effective treatment and valvuloplasty pressure. As the distance changes and becomes greater, the effectiveness of the therapy decreases. This increases both the time and the number of shock waves required for complete and effective treatment. Hence, there is a need for a shock wave valvuloplasty catheter that maintains therapy effectiveness at a desired level until the valve being treated is dilated the desired amount.